Racket stringing machine

ABSTRACT

A racket stringing machine which includes a turntable for supporting the racket to be strung in a given plane, a capstan for receiving and tensioning the string being strung on the racket and a motor mounted on a rotatable bracket and coupled to the capstan for rotating the capstan to tension the spring, the tension of the string causing the motor bracket to rotate against a resilient bias to operate a switch when the preselected amount of tension is applied to the string thereby deenergizing the motor.

United States Patent [191 Kaminstein [451 Nov. 11, 1975 I RACKETSTRINGING MACHINE [76] Inventor: Bernard Kaminstein, 329 Franklin Place,Paramus. NJ. 07652 Filed: Mar. 15, 1974 [211 App]. No.: 451,428

[56] References Cited UNITED STATES PATENTS 1.877.171 9/1932 Hallenbeck254/173 UX 1.962.865 6/1934 Goodhall et a1. 273/73 A 2.262.110 11/1941Mineck 273/73 A X 2.292.738 8/1942 Bonney 254/174 2.309.849 2/1943Kausal et a1.. 273/73 A 2.636.953 4/1953 Hunt 254/174 X 3.052.878 9/1962Berry 254/174 X 3.302.950 2/1967 Hartman... 273/73 A 3.441.275 4/1969Held 273/73 A 3.511.502 5/1970 Spenle 273/73 A 3.538.763 11/1970Amtsberg et a1 73/136 R 3.635.080 1/1972 Krueger et a1.

3.675.482 7/1972 Hewitt 73/144 3.728.502 4/1973 Hawkins et a1. 254/174 XFOREIGN PATENTS OR APPLICATIONS 7.768 6/1932 Austra1ia.....- 273/73 A429.034 5/1935 United Kingdom 273/73 A Primal E.\'aminerRichard .1.Apley Attorney. Agent, or Firm-Lindenberg, Freilich, Wasserman, Rosen &Fernandez [57] ABSTRACT 13 Claims, 10 Drawing Figures TENSlON oi;SELECTOR I 1.,

Sheet 1of3 3,918,713

US. Patent 'Nov. 11,1975

Sheet 2 of 3 US. Patant Nov. 11, 1975 RACKET STRINGING MACHINEBACKGROUND OF THE INVENTION This invention relates generally to machinesfor stringing sports rackets and more particularly to machines forstringing rackets which apply a settable uniform tension to the stringof the racket.

The stringing of sports rackets, such as used for tennis or squash, isquite arduous and time consuming when done by hand. A number of racketstringing machines are available but all of them have serious drawbacksin terms of cost, complexity or mode of use which prevent them frombeing widely accepted. A typical one of these machines is that taught inUS. Pat. No. 3,635,080 which describes a very complex racket stringingmachine in which the force for tensioning the string is generated by ahydraulic cylinder. Besides the expense and complexity inherent in theuse of hydraulic systems with the associated pumps and liquid reserviorand supply systems, the machine has the added disadvantage that thehydraulically actuated string tensioning clamp can be moved only alimited distance. Thus, either the throw ofthe hydraulic cylinder mustbe quite large, thereby increasing the size and cost of the machine, orthe string must be pretensioned, either manually or by some other meansin order for the movement of the string tensioning clamp to be enough todraw the string to the proper tension. The clamping mechanism forholding the last tensioned string segment while the racket isrepositioned for tensioning the next segment is also quite complex and,more importantly, unless carefully adjusted, the string tensioning andholding clamps may either hold the string too loosely so that it slips,or too tightly, so that it is crushed.

OBJECTS AND SUMMARY OF THE INVENTION It is therefore an object of thepresent invention to provide an improved racket stringing machine.

It is a further object of the invention to provide an improved racketstringing machine in which the string may be pulled to the propertension independently of its length.

It is a still further object of the invention to provide an improvedracket stringing machine capable of applying a settable uniform tensionto the stringing which is much simpler in construction and use thanthose of the prior art. In accordance with these and other objects ofthe invention, applicant provides a racket stringing machine whichcomprises a turntable for supporting and rotating the racket in a givenplane, a capstan disposed for receiving and tensioning a string beingstrung on the racket, means for rotating the capstan until a preselectedtension is applied to the string, and means for clamping the segment ofthe string tensioned by the capstan at a point proximate the interiorside of the rim of the racket on the edge of the face toward the capstanfor maintaining the tension on the segment of the string within the rimof the racket when the string is removed from said capstan.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a perspective view of theracket stringing machine according to the invention.

FIG. 2 is a perspective view of the string gripping clamp of the machineof FIG. 1.

FIG. 3 is a top view of the bottom of the racket holding turntable ofthe machine of FIG. 1.

FIG. 4 is a sectional view of the turntable of FIG. 3.

FIG. 5 is a detail drawing of the racket clamping mechanism.

FIG. 6 is a sectional view of the clamping mechanism of FIG. 5.

FIG. 7 is a sectional view of the capstan drive mechanism of the racketstringing machine according to the illustrated embodiment of theinvention.

FIG. 8 is a top view of the capstan drive mechanism of FIG. 7.

FIG. 9 is a sectional view of the capstan drive mechanism of FIG. 8.

FIG. 10 is a schematic diagram of the electrical portion of the machineof FIG. 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to FIG. 1of the drawings, the racket holding turntable 11 is rotatably mounted onthe rigid base 13 for horizontally supporting the racket 15, in thiscase a tennisracket, clamped to the top 17 thereof. The pads 18 of aresilient material such as rubber are provided on the top 17 forpreventing damage to the racket 15. The string 19 with which the racket15 is being strung is tensioned by means of the capstan 21 rotatablymounted in the supporting housing 23 which is affixed to the base 13.

An ON-OFF switch 27 for starting and stopping the tensioning action ofthe capstan 21 and a dial 29 for setting the desired amount of tensionare provided on the housing 23. Also provided on the housing 23 is apilot light 31 which, in the illustrated embodiment, lights only whencapstan 21 is rotating to increase the tension on the string 19.

A string clamping assembly 33 is rotatably mounted on the base of theturntable 11 for clamping the last tensioned segment of the string 19proximate the interior side of the rim of the racket 15 at the edge ofthe racket face closer to the capstan 21 in order to maintain thetension on the string segment after the capstan tensioning force isreleased. The structure of the clamping assembly 33 can best be seen inFIGS. 2 through 4 of the drawings. The tensioned segment of the string19 is clamped between the jaws 35 and 37. Jaw 35 is formed as anextension of the channel member 39 which is pivotally mounted on theblock 41 at pin 43. The other jaw 37 is pivotally mounted on the pin 45and is biased toward the jaw 35 by the compression spring 47 which bearsagainst the channel member 39 and the extension 49 of the jaw 32. Thejaws 35 and 37 are notched to allow them to be fit around and crossedstring segments on the racket face. The mating surfaces of the jaws 35and 37 are preferably coated or roughened to increase their coefficientof friction.

The actuating member 51 is pivotally mounted on the channel member39'and when depressed bears against the extension 49 of the jaw 37 forrotating the jaw 37 against bias to open the jaws.

The block 41 is slidably and pivotally mounted on the rod 53. The holein the block 41 into which the shaft 53 fits is preferably very closefitting so that a minimum of play exists between the block 41 and therod 53.

FIGS. 3 and 4 show the bottom plate of the turntable 11 and the mountingof the rod supporting and positioning trough 55. For the sake of clarityof illustration the channel member 39 is not shown in FIG. 3. The trough55 is rotatably mounted substantially at the center of the bottom plateof the turntable 11. The rod 53 is fixidly mounted in the sides of thetrough 55 at a position offset from the center of the bottom plate. Thetrough 55 may be locked in any one of four orthoginal positions withrespect to the turntable 11 by the spring biased clamp 57 which isspring biased downwardly to mate with one of the holes 59 in the bottomplate of the turntable 11. In these four positions the rod 53 isalligned with the main (parallel to the racket handle) or cross stringsof the racket 15 clamped to the top 17 of the turntable 11 and is offseton one or the other side of center of the racket 15 by a distancepreferably on the order of one fourth of the average of the length andwidth of the racket face.

Referring to FIGS. 1 and 4, the turntable 11 may be locked to the base13 in any position by the frictional material 61 which is eccentricallymounted on the shaft 63. The shaft 63 is coupled to and controlled bythe knob 64. After positioning the turntable 11 in the desired positionthe operator turns the knob 64 to bring the frictional material 61(which may be rubber) into engagement with the bottom of the turntable11 thereby preventing further rotation. Thus segments of the string 19strung in all four directions may be tensioned by the capstan 21. Theracket 15 is clamped to the top 17 of the turntable 11 by means of theclamps 25, one of which is illustrated in FIGS. and 6 of the drawings.The clamps 25 include an L-shaped racket gripping member 65 positionedin the knotch 67 in the frame 11. The threaded portion 69 of thegripping member passes through the hole 71 in the rod 73 and is inthreaded engagement with the thumb screw 75. The shoulder 77 on theL-shaped member 65 limits the distance that the member 65 can drop whenno racket is on the turntable 11. The rod 73 is pivotally mounted by thepin 79 the underside of the top 17 of the turntable 11. The tensionspring 81 biases the end of the rod 73 in which the gripping member 65is mounted away from the side of the turntable 11 toward a racketrelease and insertion position. The rod 73 may be pivoted against biasto bring the gripping member 65 into engagement with the racket by meansof the thumb screw 83 which is threaded through the hole in the side ofthe turntable 11 and bears against the rod 73 proximate the other endthereof. To clamp the racket 15 to the turntable 11, the racket 15 isfirst positioned with the gripping members 65 within the rim proximateand opposite to the throat of the racket 15. The thumb screws 83 arethen rotated to cause the gripping members 65 to engage the rim and tostretch the racket 15 slightly. After this, the thumb screws 75 aretightened to cause the gripping members 65 to clamp the racket 15 firmlyagainst the top 17 of the turntable 11. The mechanism which rotates thecapstan 21 until a preset tension is exerted on the string 19 forms animportant feature of the machine of the present invention. As can beseen in FIGS. 7, 8 and 9, the capstan 21 is mounted on the shaft 85which is journaled in the sides of the supporting housing 23 by thebearings 87. The motor support and microswitch actuator member 89includes a rigid rectangular portion 91 which is rotatably mounted onthe shaft 85 and a motor support bracket 93 affixed to the portion 91.The motor 95 is mounted on the motor support bracket 93 for movementwith the portion 91 and drives the drive gear 97 which is affixed to itsshaft 99. The drive gear 97 engages the capstan gear 101 which isaffixed to the shaft for rotating the capstan 21 to exert tension on thestring 19.

The member 89 is biased in the clockwise direction as seen in FIG. 7 bythe compression spring 103 which bears with one end against theextension 105 of the motor support bracket 93 and with the other end.

against the bracket 107. i

The motor control microswitch 109 is mounted on the microswitch positioncontrol gear 111 which is rotatably mounted on the bracket 107. Acertain amount of friction is provided in the mounting of the gear 111so that the actuation of the microswitch 109 by the extension 105 of themotor support bracket 93 does not cause a rotation of the gear 111. Theposition of the microswitch 109 is controlled by the knob 29 (FIG. 1)

through the shaft 113 and the pinion gear 115 which engages the gear111. The extension 105 of the bracket 93 includes an activating portion117 extending toward 1 switch 109 toward or away from the actuatingportion 1 1 17 and decreases or increases, respectively, the presettension to be exerted on the string 19 by the capstan 21. The capstan 21includes a sleeve 119 of a resilient material such as 20 durometerneoprene rubber.

Referring now to FIG. 10 of the drawing, the ON- OFF switch 27 isconnectedin a series circuit with the microswitch 109, the motor 95 andthe line voltage.

supply. The indicator lamp 31 is connected across the motor 95 andindicates when power is supplied thereto.

In order to tension the string 19 its end is wrapped around the capstan21, preferably with a portion of the string 19 on the capstan 21 passingover a portion closer to the end thereof so that the string isselflocking on the resilient sleeve 119 of the capstan 21. When theswitch 27 is turned on, the motor 95 starts and rotates the capstan 21in a clockwise direction as viewed in FIG. 1 thereby turning the string19 wrapped there- I about. As the tension exerted on the string 19increases, the rotational force of the motor 95 coupled through thegears 97 and 101 to the capstan tends both to rotate the capstan 21 inthe clockwise direction and i to rotate the motor support andmicroswitch actuator member 89 against the bias of the compressionspring 103 in the clockwise direction as seen in FIG. 7. The rotation ofthe member 85 swings the actuating portion 117 toward the microswitchuntil, when the tension on the string is equal to the desired amount seton the dial.

29 (FIG. 1), the actuating portion 117 actuates the microswitch 109thereby removing power from the motor 95 and the indicator lamp 31. Thetension on the string 19 (usually between 40 and 60 pounds) is enough torotate the capstan 21 and the motor drive gear 97 in the oppositedirection so that the actuating member 117 swings away from themicroswitch 109 thereby causing I it to close again and reenergize themotor 95. This again rotates the capstan 21 in the clockwise directionuntil the actuating portion strikes the microswitch 109. This process ofrepeated incremental tightening and loosening of the string 19 continueswith the indicator lamp 31 flashing on and off thereby indicating to theopertor that the string 19 is tensioned by the preset amount.

The operator then clamps the tensioncd portionof the string [9 betweenthe jaws 35and37 of the string clamping assembly 33 at the pointimmediately interior to the rim of the racket on the edge of the facetoward the capstan 21. The switch 27 is then turned off and the string19 is unwound from'the capstan 21. The force exerted by the tcnsionedsegment of the string 19 on the jaws 35 and 37 tends to cock the block41 on the rod 53 thereby locking thc block 4 in position so that itcannot slide along the rod 53.

The operator next threads the string l9 along the next segment of itspath, rotates thefrictionalmatrial 61 out of engagcmentwith theturntable l 1, rotates the turntable 11 to the proper position fortensioning the' next segment. and reengages the frictionsl material 61.He then procedes as before, wrapping the string about the capstan 21 andturning on the switch 27. After this next segment is tensioned by themotor 95 acting through the capstan 21, the operator removes theclamping assembly 33 from the previous segment and clamps the newsegment in the manner explained above.

The offset of the rod 53 with respect to the center line of the lengthor width of the face of the racket l5 clamped on top of the turntable 11decreases the maximum extension of the block 41 and the channel member39 needed to reach any part of the face of the racket l5 and therebyminimizes the inherent backlash of the clamping system 33.

As is apparent to one skilled in the art the components of the stringingmachine according to the illustrated embodiment of the invention uponwhich forces are exerted during the tensioning of the string 19 must bestrong enough to withstand these forces without excessive deformation.The required strength of the various components may be easily determinedby experimentor by calculation, working from the knowledge of thetension to be exerted on the string 19.

The above description a preferred embodiment of the invention is givenby way of illustration only and, as will be apparent to one skilled inthe art, changes in detail can be made without departing from the spiritof the invention whose scope is defined by the appended claims.

What is claimed is:

l. A racket stringing machine comprising:

a turntable for supporting and rotating a racket to be strung in a givenplane, said turntable including means for clamping said racket thereto;

capstan means disposed for receiving and tensioning a string beingstrung on said racket;

means for establishing a value of a tension desired to be applied tosaid string by said capstan means,

means for rotatiang said capstan means in a direction to increase thetension applied to a string received thereon;

means responsive to said string reaching said desired value of tensionfor deenergizing and energizing said means for rotating said capstanmeans to incrementally loosen and tighten said string; and

means for clamping the segment of the string tensioned by the saidcapstan means at a point proximate the interior side of the rim of theracket on the edge of the racket face closer to said capstan 6 2.Therackct stringing machineofclaim I wherein said capstan means includesa sleeve of resilient material for preventing slippage of said stringduring tensioning. w

3'. The racket stringing machine of claim I wherein said meansfor'elamping cludes:-'-

"a clamp'base rotatably mounted in said turntable;

a rod fixidly mounted to said clamp base substantially parallel'to theplane of the face ofa racket clamped to said turntable; and u a clampingmember slideably mounted on said rod.

4. The racket stringing machine of claim 3wherein said rod is offsetfrom'the center of said turntable.

5. The racket stringing machine of claim 4 wherein said clamp baseincludesmeans settable for fixing said clamp base in four orthoginalpositionswith said rod parallel to'the main and cross strings of aracket clamped to said turntable on either side of the center of saidturntable.

6. The racket stringing machine of claim 3 wherein said clamping memberincludes a block member slideably and rotatably mounted on said rod anda pair of coactingjaws pivotally mounted on said block member.

7. The racket stringing machine of claim 6 wherein said jaws includespring means for biasing them towards a closed position.

8. The racket stringing machine of claim 7 further including means forfixing said turntable in selected positions with respect to said clampbase.

9. A racket stringing maching comprising:

a turntable for supporting and rotating a racket to be strung in a givenplane, said turntable including means for clamping said racket thereto;

capstan means disposed for receiving and tensioning a string beingstrung on said racket;

means for rotating said capstan means until a preselected tension isapplied to said string, including motive means;

means for operatively coupling said motive means to said capstan meansfor rotating said capstan to tension as string wrapped thereunder;

switch means for controlling the energization of said motive means;

a rotatable bracket for mounting said motive means,

said bracket including a portion disposed for actuating said switchmeans to deenergize said motive means; and

means for resiliently biasing said bracket to a rest position in whichsaid actuating portion is remote from said switch means, the tensioningof string by the rotation of the capstan means acting to cause saidbracket to rotate against bias to swing said actuating portion towardsaid switch means for deactivating said motive means when the tension ofsaid string reaches a preselected level; and

means for clamping the segment of the string tensioned by the saidcapstan means at a point proximate the interior side of the rim of theracket on the edge of the racket face closer to said capstan formaintaining the tension on the segment of said spring within the rim ofthe racket when the string is removed from said capstan means.

10. The racket stringing machine of claim 9 further including means formoving said switch means towards or away from the rest position of saidactuating portion of said bracket for varying the distance which saidactuthc segmen t. of the string in- 7 ation portion must travel againstbias to actuate said switch means and thereby vary said preselectedtension.

11. The racket stringing machine of claim 10 wherein said means formoving said switch means includes a wheel on which said switch means ismounted the plain of said wheel being substantially parallel to theplain of motion of said actuating portion and means for rotating saidswitch means.

12. In a racket stringing machine, the combination comprising:

a capstan for tensioning a string wrapped therearound;

motive means operatively coupled to said capstan for rotating saidcapstan to exert tension on said string; switch means for controllingthe energinization of said motive means;

a rotatable bracket for mounting said'motive means;

means movcable with said bracket and disposed for actuating said switchmeans to deenergize said motive means; and

means for resiliently biasing said bracket to a rest position in saidmeans movable with said bracket is 13. The racket stringing machine ofclaim 12 further i including means for moving said switch means towardsor away from the rest position of said actuating means for varying thedistance which said actuating means must travel against bias to actuatesaid switch means and thereby vary said preselected tension.

1. A racket stringing machine comprising: a turntable for supporting androtating a racket to be strung in a given plane, said turntableincluding means for clamping said racket thereto; capstan means disposedfor receiving and tensioning a string being strung on said racket; meansfor establishing a value of a tension desired to be applied to saidstring by said capstan means, means for rotatiang said capstan means ina direction to increase the tension applied to a string receivedthereon; means responsive to said string reaching said desired value oftension for deenergizing and energizing said means for rotating saidcapstan means to incrementally loosen and tighten said string; and meansfor clamping the segment of the string tensioned by the said capstanmeans at a point proximate the interior side of the rim of the racket onthe edge of the racket face closer to said capstan means for maintainingthe tension on the segment of said string within the rim of the racketwhen the string is removed from said capstan.
 2. The racket stringingmachine of claim 1 wherein said capstan means includes a sleeve ofresilient material for preventing slippage of said string duringtensioning.
 3. The racket stringing machine of claim 1 wherein saidmeans for clamping the segment of the string includes: a clamp baserotatably mounted in said turntable; a rod fixidly mounted to said clampbase substantially parallel to the plane of the face of a racket clampedto said turntable; and a clamping member slideably mounted on said rod.4. The racket stringing machine of claim 3 wherein said rod is offsetfrom the center of said turntable.
 5. The racket stringing machine ofclaim 4 wherein said clamp base includes means settable for fixing saidclamp base in four orthoginal positions with said rod parallel to themain and cross strings of a racket clamped to said turntable on eitherside of the center of said turntable.
 6. The racket stringing machine ofclaim 3 wherein said clamping member includes a block member slideablyand rotatably mounted on said rod and a pair of coacting jaws pivotallymounted on said block member.
 7. The racket stringing machine of claim 6wherein said jaws include spring means for biasing them towards a closedposition.
 8. The racket stringing machine of claim 7 further includingmeans for fixing said turntable in selected positions with respect tosaid clamp base.
 9. A racket stringing maching comprising: a turntablefor supporting and rotating a racket to be strung in a given plane, saidturntable including means for clamping said racket thereto; capstanmeans disposed for receIving and tensioning a string being strung onsaid racket; means for rotating said capstan means until a preselectedtension is applied to said string, including motive means; means foroperatively coupling said motive means to said capstan means forrotating said capstan to tension as string wrapped thereunder; switchmeans for controlling the energization of said motive means; a rotatablebracket for mounting said motive means, said bracket including a portiondisposed for actuating said switch means to deenergize said motivemeans; and means for resiliently biasing said bracket to a rest positionin which said actuating portion is remote from said switch means, thetensioning of string by the rotation of the capstan means acting tocause said bracket to rotate against bias to swing said actuatingportion toward said switch means for deactivating said motive means whenthe tension of said string reaches a preselected level; and means forclamping the segment of the string tensioned by the said capstan meansat a point proximate the interior side of the rim of the racket on theedge of the racket face closer to said capstan for maintaining thetension on the segment of said spring within the rim of the racket whenthe string is removed from said capstan means.
 10. The racket stringingmachine of claim 9 further including means for moving said switch meanstowards or away from the rest position of said actuating portion of saidbracket for varying the distance which said actuation portion musttravel against bias to actuate said switch means and thereby vary saidpreselected tension.
 11. The racket stringing machine of claim 10wherein said means for moving said switch means includes a wheel onwhich said switch means is mounted the plain of said wheel beingsubstantially parallel to the plain of motion of said actuating portionand means for rotating said switch means.
 12. In a racket stringingmachine, the combination comprising: a capstan for tensioning a stringwrapped therearound; motive means operatively coupled to said capstanfor rotating said capstan to exert tension on said string; switch meansfor controlling the energinization of said motive means; a rotatablebracket for mounting said motive means; means moveable with said bracketand disposed for actuating said switch means to deenergize said motivemeans; and means for resiliently biasing said bracket to a rest positionin said means movable with said bracket is remote from said switchmeans, the tensioning of said string by the rotation of said capstanacting to cause said bracket to rotate against bias to swing saidactuating means toward said switch for deenergizing said motive meanswhen the tension of said string reaches a preselected level.
 13. Theracket stringing machine of claim 12 further including means for movingsaid switch means towards or away from the rest position of saidactuating means for varying the distance which said actuating means musttravel against bias to actuate said switch means and thereby vary saidpreselected tension.